> ## Documentation Index
> Fetch the complete documentation index at: https://kleros-mintlify-6ebc7975.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Smart Contracts

> Reference for Proof of Humanity V2 smart contracts, covering the IProofOfHumanity interface, identity queries, and registration lifecycle functions.

## Core Interface

The `IProofOfHumanity` interface exposes the functions needed to query and interact with the PoH V2 registry.

### Identity Queries

```solidity theme={null}
/// @dev Returns true if the address is registered as a verified human.
/// Checks both V2 registrations and V1 via Fork Module.
function isHuman(address _account) external view returns (bool);

/// @dev Returns the humanityId bound to an address.
/// Returns bytes20(0) if the address is not registered.
function humanityOf(address _account) external view returns (bytes20);

/// @dev Returns the address currently bound to a humanityId.
/// Returns address(0) if the humanityId is not claimed.
function boundTo(bytes20 _humanityId) external view returns (address);

/// @dev Returns true if the humanityId is currently claimed by any address.
function isClaimed(bytes20 _humanityId) external view returns (bool);
```

### Registration Functions

```solidity theme={null}
/// @dev Submits a new registration claim.
/// Requires payment of the registration deposit.
function claimHumanity(bytes20 _humanityId, string calldata _evidence) external payable;

/// @dev Vouches for a pending registration.
/// Voucher must be a registered human.
function vouch(address _claimer, bytes20 _humanityId) external;

/// @dev Challenges a pending or existing registration.
/// Creates a dispute in Kleros Court.
function challengeRequest(
    bytes20 _humanityId,
    uint256 _reason,
    string calldata _evidence
) external payable;
```

***

## Cross-Chain Interface

The `ICrossChainProofOfHumanity` contract mirrors identity state on foreign chains. It exposes the same read functions:

```solidity theme={null}
interface ICrossChainProofOfHumanity {
    function isHuman(address _account) external view returns (bool);
    function isClaimed(bytes20 _humanityId) external view returns (bool);
    function humanityOf(address _account) external view returns (bytes20);
    function boundTo(bytes20 _humanityId) external view returns (address);
}
```

State updates are propagated from the home chain (Gnosis) to foreign chains through bridge transactions.

***

## Data Structures

### Humanity

Each registered human is represented by a `Humanity` struct containing the registration state:

| Field               | Type      | Description                                        |
| ------------------- | --------- | -------------------------------------------------- |
| `owner`             | `address` | Current wallet address bound to this humanity      |
| `humanityId`        | `bytes20` | Unique soulbound identifier                        |
| `expirationTime`    | `uint40`  | When the registration expires and requires renewal |
| `nbPendingRequests` | `uint256` | Number of active registration or renewal claims    |

### Challenge Reasons

Challenges must specify a reason code:

| Code | Reason              | Description                                                      |
| ---- | ------------------- | ---------------------------------------------------------------- |
| 0    | None                | Invalid                                                          |
| 1    | IncorrectSubmission | Profile does not meet registration policy requirements           |
| 2    | Deceased            | The registered human is deceased                                 |
| 3    | Duplicate           | The submitter is already registered under a different humanityId |
| 4    | DoesNotExist        | The submitter does not exist or the video is fabricated          |

***

## Events

```solidity theme={null}
/// @dev Emitted when a new registration claim is submitted.
event ClaimRequest(address indexed _requester, bytes20 indexed _humanityId);

/// @dev Emitted when a claim is challenged.
event ChallengePeriodRestart(
    bytes20 indexed _humanityId,
    uint256 indexed _requestId,
    uint256 _challengeId
);

/// @dev Emitted when a registration is confirmed after the challenge period.
event HumanityClaimed(bytes20 indexed _humanityId, address indexed _owner);

/// @dev Emitted when a registered human is removed (revocation or expiry).
event HumanityRevoked(bytes20 indexed _humanityId, address indexed _owner);
```

***

## Dispute Integration

When a registration is challenged, PoH creates a dispute in Kleros Court with the following parameters:

| Parameter      | Value                                             |
| -------------- | ------------------------------------------------- |
| **Arbitrator** | KlerosCore on the home chain                      |
| **Court**      | Humanity Court (courtId configured at deployment) |
| **Choices**    | 2 (Accept Registration / Reject Registration)     |
| **Ruling 0**   | Refuse to arbitrate                               |
| **Ruling 1**   | Accept -> registration is valid                   |
| **Ruling 2**   | Reject -> registration is invalid                 |

Evidence is submitted on-chain and displayed in the Court V2 interface. The dispute template specifies the PoH registration policy as the primary document for juror evaluation.